Browsing by Author "Golias, Michael"
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- ItemAbsorption and desorption properties of fine lightweight aggregate for application to internally cured concrete mixtures(ELSEVIER SCI LTD, 2011) Castro, Javier; Keiser, Lucas; Golias, Michael; Weiss, JasonRecently, substantial interest has developed in using fine lightweight aggregate for internal curing in concrete. Mixture proportion development for these mixtures requires the specific gravity, water absorption, and water desorption characteristics of the aggregate. This paper presents results from a recent study in which the properties of commercially available expanded shale, clay and slate lightweight aggregates (LWA's) were measured. This research measured the time-dependent water absorption response for the lightweight aggregate. The results indicate that a wide range of 24 h water absorption values exist for commonly used fine lightweight aggregates (e.g., absorption between 6% and 31%). Desorption was measured and it was found that between 85% and 98% of the 24 h absorbed water is released at humidities greater than 93%. These properties can be normalized so that they can be efficiently used in proportioning concrete for internal curing. Normalized plots of absorption and desorption demonstrate benefits for a single function that describes a large class of expanded shale, clay, and slate aggregate for use in internal curing. (C) 2011 Elsevier Ltd. All rights reserved.
- ItemThe influence of the initial moisture content of lightweight aggregate on internal curing(ELSEVIER SCI LTD, 2012) Golias, Michael; Castro, Javier; Weiss, JasonThis paper explores the potential for manufacturing internally cured concretes with lightweight aggregate (LWA) that has different initial moisture contents prior to mixing: oven-dry, 24 h pre-wetted, and vacuum saturated. Results show that when LWA is used in an oven-dry condition it can absorb water from the paste prior to set which will be returned to the system as internal curing water. When mixture proportion adjustments are properly made to account for the water absorbed by the aggregate before setting, the mixture can provide internal curing benefits. These beneficial aspects include increased hydration which leads to higher compressive strength, reduced water absorption, and reduced electrical conductivity (permeability). Further, these benefits include reduced autogenous shrinkage and a lower propensity for early-age cracking. (C) 2012 Elsevier Ltd. All rights reserved.